Thermostatic switch device



Oct. 24, 1944. F. R. BEAN 2,360,842

THERMOSTATIC SWITCH DEVICE l Filed May 13, 1941 42 A FIG. I 37 5gg 5o 2O 4o 42 39 34 35 /2/ ZZ V20 1.9 '3 l M//l 14 rl l /IO y ,l C /26 FIGZ 34 373.3 .as 1o a9 ls ZI fr 44 vx g I4 l Q 3i www FRANK ROBERT EAN INVENTOR BY jwa.

Patented Oct. 24, 1944 THERMOSTATIC SWITCH DEVICE Frank Robert Bean, Rochester, N.

Y., assignor to F. A. Smith Manufacturing Company, Rochester, N. Y.

Application May 13, 1941, Serial No. 393,149

(Cl. 20G- 138) 14 Claims.

The present invention relates to a thermostatic switch device and more particularly to a simple and rugged construction for a snap-acting thermostatic switch.

While thermostatic and snap-acting thermostatic. switches are well known, they are in general of complicated design and costly construction or are unreliable in operation or in maintaining constancy of operating characteristics.

The primary object of the present invention is the provision of a thermostatic switch of sim ple and inexpensive construction but which is reliable in operation and of constant and uniform calibration in spite of variations in ambient temperature or long intervals between operation of the switch.

Another object of the invention is the provision of a thermostatic switch comprising a base, a contact assembly, a switch assembly, and a cover member, all of which can be easily and rapidly assembled to constitute a switch of uniform and deiinite operating characteristics.

A further object is the provision oi' a switch assembly including a terminal stud with a noncircular portion and a switch arm on said stud and welded thereto in predetermined relation to the non-circular portion thereof.

Still another object is the provision of a contact assembly including a terminal stud with a non-circular portion and a head thereon, and a contact fastened to said head preferably by welding, in eccentric relation to said stud and in predetermined relation to the non-circular portion thereof.

A still further object of the invention is the provision of a thermostatic switch comprising a base provided with a pair of non-circular open- Aings adapted to receive and co-operate with the non-circular portions of the terminal studs of the respective switch and contact assemblies whereby said assemblies may be readily mounted on said base in proper relation to each other and whereby the spacing between said terminal studs is greater than the length of the switch arm.

Another object vis the provision of a thermostatic switch assembly including a. snap-acting switch arm normally engaging a contact and a cover member having an abutment for limiting the snap movement of said switch arm away from said contact.

A further object of the invention is the provision of a switch assembly including a dished and slotted snap-acting thermostatic element which has one or more relatively inert portions at which said element is welded to the terminal stud and/or to a contact thereon.

Other and further objects of the invention will be mentioned or will be apparent to those skilled in the art by the following description.

The aforementioned and other objects of the invention are embodied in a thermostatic switch device comprising a base'plate provided with a pair of spaced non-circular openings, one of 'which is larger than the other, a switch arm assembly including a terminal stud fastened to said base plate and having a non-circular portion within the smaller non-circular opening in said base plate and including a snap-acting thermostatic switch arm fastened at one end to said stud and having a contact on its other end, a contact assembly including a terminal stud having a head carrying a contact eccentrically located with respect to said stud and having a non-circular portion within and spaced from the larger opening in said base plate, an insulating bushing around said non-circular portion of said contact assembly and within the larger opening in said base plate, and a cover member fastened to said base ,plate and having an abutment extending toward the contact carrying end of said switch arm toA limit the snap-acting movement thereof.

Reference is now made to the accompanying Y drawing wherein similar reference characters designate similar elements and wherein:

Fig. 1 is an end view o1' the thermostatic switch device according to the invention.

Fig. 2 is a vertical cross-section of said thermostatic switch device taken on the line 2-2 of Fig. 1.

Fig. 3 is a plan view of the thermostatic switch device with the cover member` removed.

Fig. 4 is a plan view of the switch assembly of my thermostatic switch device.

Fig. 5 is an exploded perspective of the switch device of the present invention.

In the illustrated embodiment of the invention, the thermostatic switch device comprises a base. a contact assembly, a switch assembly, and a cover member all of which will be specifically described hereinafter but which, except for the essential features defined in the claims, may vary considerably in details of construction.

The base may comprise a metallic base plate I0 having an angular bracket portion II which is provided with holes I2 and by means of which the switch device may be mounted in any suitable position. Said base is provided with a pair of non-circular openings in which the contact and switch assemblies are mounted. As shown,

2 the metallic base plate Ill is provided with a square opening I3 and with a larger square opening I4 spaced therefrom. Base plate I0 may also be provided along its margins with apertures I5 for a purpose to be later described.

The contact assembly comprises a terminal stud I6 having a threaded portion I1, a noncircular or square portion I8, and a head I9 and also includes a contact 29 which is fastened to said head I9, preferably by welding, in a position which is eccentric to said stud I6.

If, as shown, the base plate I9 is metallic or of an electrical conducting material, the mounting of said contact assembly or said switch assembly on the base must also insulate at least one of such assemblies from the base. For instance, the contact assembly is insulated from the base by an insulating washer 2I which is placed on the stud I6 or square portion I8 thereof between the head I9 and the base plate l0 and which may be provided with a square opening 22. A noncircular insulating member has an outer contour corresponding to the non-circular opening in the base and is provided with an opening complementary to the non-circular portion of the stud of the contact assembly. Such an insulating member may be a square insulating bushing 23 which ilts into the larger opening I4 in base plate I9 and which is provided with a square opening 24 for receiving vthe square portion I8 of terminal stud I6. An insulating paper sheet 25 with flaps 26 and 21 and an insulating plate 28 complete the insulation, are placed adjacent the other side of base plate I9, and are provided respectively with spaced holes 29 and 30 through which the terminal studs of the contact and switch assemblies extend. A washer 3I and nut 32 are placed upon the terminal stud I6 and the nut 32 is tightened to secure the contact assembly to the base. It should be noted that portions or the corners of head I9 extend beyond the larger square opening I4, see Fig. 3, so that when nut 32 is tightened the pressure of said head is at least partially exerted directly upon the base plate I0 and the insulating washer 2i is under a compressive stress rather than shear and insulating bushing 23 is not compressed.

The switch assembly comprises a terminal stud and a switch arm fastened thereto.l Such a terminal stud 33 has a flange 34, a non-circular or square portion 35 adjacent thereto, and a threaded portion 36. The switch arm may be of any known thermostatic type or such as to move as the temperature thereof changes. Preferably such switch arm is of the snap-acting type so as to minimize arcing when contact is broken and may be composed of bimetallic material. As shown, the bimetallic switch arm 31 is rectangular in outline and is dished to be concave on the side of the metal having the greater coeiilcient of expansion. Said switch arm 31 is provided with two diverging slots 38 and is gathered to form the crimped portions 33 at the end of each slot and at the corners of the arm 31. Said crimped portions 39 in the bimetallic arm 31 give the same its concave formation so that, when heated to a predetermined temperature,

said switch arm 31 abruptly reverses its curva- .ture in a well understood manner.

When the switch arm 31 is formed in the manlner just described, there are one or more points thereon which are relatively inert or which may be called dead spots. One such relatively inert portion oi.' switch arm 31 is located between said crimped portions 39 and another occurs at the 7g switch arm 31 when it snaps opposite end of arm tact 40 is fastened inert portions preferably by a spot weld 4I. The.

switch arm 31 is also mounted upon the terminal stud 33 at another such dead spot. The end of terminal stud 33 may be turned down to a ferrule which is inserted through arm 31and spun over to form a rivet 42. A pair of spot welds 43 are made between switch arm 31 and terminal stud 33 adjacent rivet 42 and such welds 43 prevent arm 31 from rotating with respect to stud 33 around the rivet 43 andalso increase the conductance or decrease the millivolt drop between said switch arm 31 and terminal stud 33. Furthermore, since the spot welds 4I and 43 are in relatively inert portions of switch arm 31, any loss of temper or strains set up in arm 31 by the welding do not aiect the operation or operating characteristics of said thermostatic switch arm 31.

The terminal stud 33 of the switch assembly extends through the non-circular or square opening I3 in the base plate I0 and also throughh'e i holes 29 and 30 in paper sheet 25 and insulating switch device is the plate 23. A washer 44 and nut 45 are placed over the threaded portion 36 of stud 33 and the nut 45 is tightened to fasten said switch assembly upon the base with said contact 40 normally or at room temperature engaging said contact 20 of said contact assembly.

One particular feature of the invention which contributes greatly to the ease of assemblying the arrangement of the non-circular portions of the terminal studs with respect to the eccentrically located contact 20 of the contact assembly and the switch arm 31 of the switch assembly so that engagement of such nonciroular portions of the studs with the non-circular openings in the base readily and precisely locates the two assemblies so that their respective contacts 20 and 40 are in good alignment when the assemblies are mounted.' upon said base. Also the eccentricity of contact 20 with respect to the terminal stud I5 permits the use of a relatively short snap-acting bimetallic switchA arm 31, which is preferable for reasons of cost and operating characteristics, but because of such eccentricity the terminal studs I6 and 33 are spaced sufficiently for ease in manipulation of the respective nuts 46 and 41 to fasten the conductor terminals 48 and 49 to said studs I3 and 33.

While the non-circular openings in the base and the noncircular portions on the terminal studs are shown as square, it must be understood that such openings and stud portions may be. of any form to co-operate' with each other and deflnitely located said contact and switch assemblies in predetermined positions upon the base. Furthermore, the non-circular openings in the base may be of the same size if there is no' need of insulating the terminal stud from the base or if the base ismade if insulating material.

For the purpose of protecting the switch device from dirt and/or damage; and for providing a back stop for the switch arm, a cover member 5I! is placed over the switch device. Such a. cover member 50 is channel-shaped and has a plurality of tongues 5I which extend through the apertures I5 in the b ase plate I0 and which may be bent over as shown in Fig. 1 to fasten said cover member 50 to the base plate I0. An abutment is formed from said cover member 50 as by embossing a strip 52 with a boss 53 from said cover member 50. Said strip 52 extends inwardly of cover member 50 and the .boss 53 is located to engage the back of into its, reversed position and to limit the amount of such reversal. By providing such an abutment, the time for reengagement of the switch can be controlled and said time for re-engagement may be regulated by further deformation of said strip 52 to change the position of boss 53 either nearer to switch arm 3l to shorten the time of re-engagement or farther away from switch arm 3l to lengthen said time of re-engagement.

Since many modifications of said thermostatic switch device may be made without departing from the spirit of the invention, the present disclosure is to be considered as illustrative and the scope of the invention is defined in the appended claims.

I claim:

1. A thermostatic switch device comprising a base, a contact assembly on said base including a contact, a switch assembly on said base and including a thermostatic switch arm having a, contact end normally engaging said contact and, when heated to a predetermined temperature, moved out of engagement with a cover member' on said base and having an integral deformable portion opposite the -contact end of said switch arm to limit its movement away from said contact.

2. A thermostatic switch device comprising a base provided with a pair openings having their centers in spaced relation, a switch assembly including a thermostatic switch arm carrying a con tact and having an effective length less than the spacing between the centers of said openings and including a terminal stud extending through one of said openings and fastened to said baue, and a contact assembly including a head, a second terminal stud extending through the other of said openings and fastened to said base, and a contact xed cn said head and eccentrically located with respect to said second terminal stud in the direction toward the rst mentioned stud with the center of the contact on said head substantially opposite the center of the Contact on said switch arm.

3. A thermostatic switch device comprising a base provided with a pair of spaced openings, a contact assembly including a head, a termina-l stud having a center line and extending through one of said openings in said base, and a contact on said head and with its center eccentrically located with respect to said center line, and a switch assembly including a terminal stud also having a center line and extending through the other opening in said .base and including a thermostatic switch arm on said stud and having a contact point for engaging said contact, the eccentricity of said contact extending toward the studv of said switch assembly so that the spacing of the center lines of said terminal studs is greater than the distance on said switch arm from its Contact point to the center line of said terminal stud of said switch assembly.

4. A thermostatic switch device comprising a base provided with a pair of spaced non-circular holes, a contact assembly on said base and including a head, a non-circular portion complementary to one of said holes, and a contact on said head and eccentric to said portion in the direction toward said other hole when said portion is within said one hole, and a switch assembly on said base and including a stud having a non-circular portion 'complementary to said other hole and a switch arm fastened to said stud in relative position to the portion thereof to extend toward said contact.

said contact, and

switch device comprising a pair of spaced non-circular holes, and a contact assembly on said base and including a head, a non-circular portion complementary to one of said holes, and a contact on said head and eccentric to said portion in the direction toward said other hole when .said portion is within said one hole.

6. A thermostatic switch device comprising a base plate of conducting material and provided with a non-circular hole, a contact assembly on said base and including a head and a noncircular portion complementary to but smaller than said hole, and a non-circular bushing around said portion and within said hole and composed of an insulating material.

7. A thermostatic switch device comprising a base plate of conducting material and provided with a non-circular hole, a contact assembly on said base and including a head and a non-circular portion complementary to but smaller thanV said hole, a non-circular bushing around said portion and within said hole and composed of an insulating material, and a pair of insulating members on each side of said base plate andlarger than said hole therein.

8. A thermostatic switch device comprising a base plate of conducting material and provided with a non-circular hole, a contact assembly on said base and including a head and a stern having a non-circular portion complementary to but smaller than said hole, a non-circular bushing around said portion and within said hole and composed of an insulating material, an insulating washer between said head and said plate and larger than said hole therein, an insulating plate on the opposite side of said base plate and covering said hole therein, and fastening means engaging said stem and for holding said head against said insulating washer.

9.'A thermostaticswitch device comprising a base plate of conducting material and provided with a polygonal hole, a contact assembly including a head and a stem attached thereto and having a polygonal portion smaller than said hole adjacent said head and having a threaded portion, an insulating bushing having a polygonal periphery complementary to said hole and provided with an opening which is complementary to the polygonal portion on said stem, an insulating washer between said head and said base plate, a nut member on the threaded portion of said stem for drawing said head and washer toward said plate, and an insulating plate between said base plate and nut member.

10. A thermostatic switch device comprising a base plate provided with a non-circular hole, a terminal stud fastened to said base plate and having a non-circular portion complementary to and within said non-circular hole, a thermostatic switch arm, a riveted connection located coaxially of said stud and for fastening said switch arm thereto, and a welded connection between said switch arm and said stud and located to one side of said riveted connection and eccentrically of said stud.

11. A thermostatic switch device comprising a base plate provided with a hole, a, terminal stud fastened to said base plate and extending through said hole for attachment to an electrical connection, a dished thermostatic switch arm provided with slots and having portions which reverse their curvature at a predetermined temperature and having a portion displaced from said slots and the area therebetween and which 5. A thermostatic base provided with a is relatively unaffected by changes in temperature, and a welded connection between said stud and said unaffected portion of said switch arm.

12. A thermostatic switch device comprising a base plate provided with a hole, a terminal stud fastened to said base plate andextending through said hole for attachment to an electrical connection, a dished and slotted thermostatic switch arm having portions which `reverse their curvature at a predetermined temperature and having portions at opposite ends thereof which are relatively unaffected by changes in temperature, a welded connection between said stud and one of said unaffected portions of said switch arm, and a contact welded to the other unaffected portion at the other end of said switch arm.

13. A thermostatic switch device comprising a base plate, a contactl mounted upon said base plate, a snap-acting thermostatic switch arm v mounted at one end on said base plate carrying at its other end a contact normally engaging said contact, and adapted to separate said contacts rapidly when heated to a predetermined tempera' ture, and a cover member attached to said base plate and having a deformable portion opposite said contact for abutting the free end of said switch arm to limit its movement away from the first-mentioned contact.

14. A thermostatic switch device comprising al base plate provided with a pair of spaced noncircular openings, one of which is larger than the other, a switch arm assembly including a terminal stud fastened to said base plate and having a non-circular portion within the smaller non-circular opening in said base plate and including a snap-acting thermostatic switch arm fastened at one end to saidy stud and having a contact on its other end, a contact assembly including a terminal stud having a head carrying a contact eccentrically located with respect to said stud and having a non-circular portion within and spaced from the larger opening in said base plate, an insulating bushing around said non-circular portion of said contactl assembly and within the Alarger opening in said base plate, and a cover member fastened to said oase plate and having an abutment extending toward the contact carrying end of said switch arm to limit the movement thereof.

ROBERT BEAN. 

